The Antarctic Impulsive Transient Antenna (ANITA) balloon experiment was designed to detect radio signals initiated by high-energy neutrinos and cosmic ray (CR) air showers. These signals are typically discriminated by the polarization and phase inversions of the radio signal. The reflected signal from CRs suffer phase inversion compared to a direct ‘tau neutrino’ event. In this paper, we study subsurface reflection, which can occur without phase inversion, in the context of the two anomalous up-going events reported by ANITA. It is found that subsurface layers and firn density inversions may plausibly account for the events, while ice fabric layers and wind ablation crusts could also play a role. This hypothesis can be tested with radar surveying of the Antarctic region in the vicinity of the anomalous ANITA events. Future experiments should not use phase inversion as a sole criterion to discriminate between down-going and up-going events, unless the subsurface reflection properties are well understood.

中文翻译：

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对异常 ANITA 事件的思考：南极地下作为一种可能的解释

南极脉冲瞬态天线 (ANITA) 气球实验旨在检测由高能中微子和宇宙射线 (CR) 空气簇射引发的无线电信号。这些信号通常通过无线电信号的极化和相位反转来区分。与直接的“tau 中微子”事件相比，来自 CR 的反射信号会发生相位反转。在本文中，我们研究了在 ANITA 报告的两个异常上行事件的背景下，可以在没有相位反转的情况下发生的地下反射。研究发现，地下层和冷杉密度反转可能合理地解释了这些事件，而冰结构层和风消融壳也可能发挥作用。可以通过对异常 ANITA 事件附近的南极地区的雷达测量来检验这一假设。